The present invention relates to a seat back structure for a vehicle and more particularly to a rear seat back structure also called a bench seat.
Such back structures currently extend between an upper edge and a lower edge and comprise:
a rigid lower crosspiece which is next to the lower edge of the structure and has two ends;
at least first and second approximately vertical rigid uprights which each extend between an upper end and a lower end, the lower ends of the uprights being fixed to the lower crosspiece; and
pivoting means which are next to the lower edge so that the structure rotates around the lower edge between an upright position and a folded down position.
The pivoting means usually take the form of pivot pins which are connected to the structure either by welding, or by screwing onto parts themselves added by welding onto the structure. In order to control the stresses of the pivot pins, this technique has the disadvantage of requiring a good quality of welding, sometimes tricky to achieve. Furthermore, even if the welds are correctly carried out, the welding operation affects the characteristics of the structure material, particularly when this structure is in aluminium. The mechanical resistance of the structure is thus reduced.
The object of the invention is to remedy the above disadvantages by supplying a structure the pivot pins of which are fixed without weakening the mechanical characteristics of the structure and this, by simple, efficient and inexpensive means.
To this end, according to the invention, the pivoting means are carried by two bases which are each added by fitting in the tubular ends of the lower crosspiece, and each of the vertical uprights is fixed by fitting at the same time in the bases and in the lower crosspiece.
Thanks to these arrangements, the assembly of the pivoting means, such as pivot pins, is obtained without welding. The stresses undergone by the pivots are transmitted to the structure without passing through welded connections. The mechanical resistance of the back structure is thus not affected.
The structure according to the invention can possibly comprise moreover one or more of the following characteristics:
the ends of the lower crosspiece are of tubular shape delimiting a housing, the base comprises a main section which is of complementary shape to that of the housing in which it is fitted and which is provided with a recess, two opposite windows being made in each of the ends of the lower crosspiece, the recesses and the two windows being of complementary shape to that of the lower ends of the vertical uprights;
the lower crosspiece and the uprights are made in aluminium, and the pivoting means are made in steel;
the pivoting means comprise two pivots which are at least in part threaded and which project beyond the ends of the lower crosspiece from the bases;
two nuts are each immobilised in a cage made in the end of each base and the pivots are screwed in the nuts; and
the main section of each base is tapped and a drilling is made in the lower end of each upright, the pivots being screwed in the bases, passing through the drillings.